Japanese Patent Laying-Open No. 2005-143259 discloses a load driving device capable of discharging residual electric charge in a capacitor provided in the input side of an inverter. The load driving device includes the capacitor provided in the input side of the inverter for driving an alternating-current motor; a discharging resistor connected to the capacitor in parallel; a boost converter converting voltage between a battery and the capacitor; an electric path connecting a high voltage side of the boost converter to the positive electrode side of the battery; a system relay opening and closing the electric path; and a limiting resistor provided at the electric path in series with the system relay.
In the load driving device, when an ignition key is turned off, electric power accumulated in the capacitor is brought back to the battery via the limiting resistor and the system relay. When voltage across the capacitor decreases, the residual electric charge in the capacitor is discharged by the discharging resistor and the alternating-current motor.
However, Japanese Patent Laying-Open No. 2005-143259 discloses no process in the case where the system relay is welded. If the system relay provided at the electric path is welded and the discharging resistor and the alternating-current motor repeatedly perform the process of discharging the capacitor, the limiting resistor may be heated excessively and be broken.